Discrete surface state related to nitrogen-vacancy defect on plasma-treated GaN surfaces

Detailed studies on the defect-related surface states of plasma-exposed n-GaN surfaces were carried out. An anomalous flat portion appeared in the metal-insulator-semiconductor capacitance-voltage characteristics for the sample exposed to H-2 plasma, corresponding to a localized peak at E-C-0.5 eV in the surface state density distribution. Atomic-force microscope and x-ray photoemission studies revealed the formation of Ga droplets on H-2-plasma-treated GaN surfaces, caused by the desorption of nitrogen atoms in the form of NHx. These results suggested that a nitrogen-vacancy-related state near the conduction-band edge was introduced on the H-2-plasma-treated GaN surface. No such effects took place on the N-2-plasma-treated GaN surfaces. (C) 2002 American Institute of Physics.